ASHP - How to know the actual COP?

cretanrunner

Thanks again to everyone. Slightly confusing when posts disappear from the thread, but I will soldier on.

The defrost strategy is clearly important. If you had low ambients of 5C minimum, do we know how much defrosting would be going on? Is there a temp above which the pump would not need to defrost?

cretanrunner

To continue on the idea about swimming pool pumps, why would they be working any harder to run UFH than to heat a pool, bearing in mind I am in Crete and the house heating season is only slightly longer than the pool heating season?

cretanrunner

And pursuing the issue of the thermal store. I think I see what you mean, Albyota, but several heat pump manufacturers recommend that you DO link to a thermal store. Is that specific to their brand or what? And once you have reached working temperature on the store is it any different to running direct? Granted it will have a long heat-up time when you first start the heating. Does it not all come down to which way gives more continuous running of the heat pump? (Complete amateur speaking BTW).

Swipe

cretanrunner wrote: »

Thanks again to everyone. Slightly confusing when posts disappear from the thread, but I will soldier on.

The defrost strategy is clearly important. If you had low ambients of 5C minimum, do we know how much defrosting would be going on? Is there a temp above which the pump would not need to defrost?

I never get defrosts on either of my units above 3-4C. And only get them above freezing when it's sleeting or snowing and the air is very humid

bernithebiker

cretanrunner wrote: »

To continue on the idea about swimming pool pumps, why would they be working any harder to run UFH than to heat a pool, bearing in mind I am in Crete and the house heating season is only slightly longer than the pool heating season?

Pool water is chlorinated, and therefore highly corrosive to metal.

Pool heat pumps usually have titanium heat exchangers. (Mine does).

bernithebiker

cretanrunner wrote: »

And pursuing the issue of the thermal store. I think I see what you mean, Albyota, but several heat pump manufacturers recommend that you DO link to a thermal store. Is that specific to their brand or what? And once you have reached working temperature on the store is it any different to running direct? Granted it will have a long heat-up time when you first start the heating. Does it not all come down to which way gives more continuous running of the heat pump? (Complete amateur speaking BTW).

Having a 1500l heat store is a great bonus. As long as it is well insulated and preferably inside the house, I say use it. The heat pump can then just work at it's full rated power for a long period (surely the most efficient way?) and will have far fewer cycles. You could even take advantage of cheap night time rates to heat only at night. My 'store' is only 80 litres (plus the underfloor + rads). I wish I had the room for a bit more.

In my main house I have a 44kW wood burning boiler with 2000 litres thermal store. (This is compulsory). However, again, I wish I had more, 4000 would be nice.

cretanrunner

bernithebiker wrote: »

Pool water is chlorinated, and therefore highly corrosive to metal.

Pool heat pumps usually have titanium heat exchangers. (Mine does).

But I was looking at using a pool pump for UFH. Presumably having a titanium heat exchanger is neither here nor there in that situation?

cretanrunner

bernithebiker wrote: »

Having a 1500l heat store is a great bonus. As long as it is well insulated and preferably inside the house, I say use it. The heat pump can then just work at it's full rated power for a long period (surely the most efficient way?) and will have far fewer cycles. You could even take advantage of cheap night time rates to heat only at night. My 'store' is only 80 litres (plus the underfloor + rads). I wish I had the room for a bit more.

Fewer cycles is what I was thinking would be good. But strangely, I have seen other comments that state you would get less cycling by connecting direct to UFH....... I'm confused.